We study wage bargaining in which the union is uncertain about the firm's willingness to pay and threat payoffs vary over time. Strike payoffs change as replacement workers are hired, as strikers find temporary jobs, and as inventories or strike funds run out. We find that bargaining outcomes are substantially altered if threat payoffs vary. If dispute costs increase in the long run, then dispute durations are longer, settlement rates are lower, and wages decline more slowly during the short run (and may even increase). The settlement wage is largely determined from the long-run threat, rather than the short-run threat.

We present a bargaining model of union contract negotiations, in which the union decides between two threats: the union can strike, or it can continue to work under the expired contract. The model makes predictions about the level of dispute activity and the form disputes take. Strike incidence increases as the strike threat becomes more attractive, because of low unemployment or a real wage drop. We test these predictions by estimating logistic models of dispute incidence and dispute composition for negotiations from 1970 to 1989. We find support for the model's key predictions, but these associations are weaker after 1981.